1. Technical Field
The present invention relates to a metal powder production apparatus and metal powder.
2. Related Art
Conventionally, a metal powder production apparatus (atomizer) that pulverizes molten metal into metal powder by an atomizing method has been used in producing metal powder. Examples of the metal powder production apparatus known in the art include a molten metal atomizing and pulverizing apparatus disclosed in JP-B-3-55522.
The molten metal atomizing and pulverizing apparatus is provided with an ejection port from which molten bath (molten metal) is ejected in a downward direction and a nozzle having a flow path through which the molten bath ejected from the ejection port passes and a slit opened into the flow path. Water is injected from the slit of the nozzle.
The apparatus of prior art mentioned above is designed to produce metal powder by bringing the molten bath passing through the flow path into collision with the water injected from the slit to thereby disperse the molten bath in the form of a multiplicity of fine liquid droplets and then allowing the multiplicity of fine liquid droplets to be cooled and solidified.
The molten bath ejected from the ejection port falls freely through the flow path and makes contact with the water. However, the route of passage of the molten bath varies with a multiple number of factors such as a flow velocity of the water, a shape of the nozzle and the like, which in turn changes the position in which the molten bath makes contact with the water.
This poses a problem in that the molten bath is changed in its dispersion, cooling and solidification conditions, thus giving rise to a variation in grain diameter or particle size distribution of the metal powder produced.
Furthermore, since the ambient air is introduced into the depressurized flow path, there is produced an air stream in the vicinity of the flow path. Upon making contact with the air, however, the molten bath may be solidified by temperature reduction or may be degenerated or degraded by oxidation, thus leaving a possibility that the resultant metal powder shows reduction in quality. In particular, this problem becomes conspicuous in the case where the molten metal contains highly active metal elements such as Ti and Al.